Novel detergent compositions

ABSTRACT

There are disclosed novel detergent compositions comprising a mixture of one or more surfactants with a unique builder for said compositions which comprises a crosslinked, water-insoluble copolymer of at least one C2-C3 olefin and at least one polycarboxyl vinyl monomer; said crosslinked, water-insoluble copolymer being a water-swellable, gel-forming material.

United States Patent Erdy [54] NOVEL DETERGENT COMPOSITIONS [72]Inventor: Nicholas Z. Erdy, New York, N.Y.

[73] Assignee: Staufier Chemical Company, York, N.Y.

[22] Filed: Aug. 28, 1970 [211 App]. No.: 68,015

New

[52] US. Cl. ..252/544, 252/89, 252/132, 252/140, 252/155, 252/523,252/525,

[51] Int. Cl. ..Clld 3/30 [58] Field of Search ..252/89, 135, 527, 525,544, 252/546, 140, 155; 260/785 R 1 Sept. 12, 1972 3,073,806 1/1963Reinhard ..252/89 X 3,208,949 9/1965 Rosnati ..2$2/89 X 3,308,067 3/1967Diehl ..252/ l 61 3,346,873 10/1967 l-lerrmann ..252/526 FOREIGN PATENTSOR APPLICATIONS 227,960 6/195 8 Australia Primary Examiner-Leon D.Rosdol Assistant Examiner-Harris A. Pitlick Attorney-Wayne C. Jaeschke,Martin Goldwasser and Daniel S. Ortiz [57] ABSTRACT There are disclosednovel detergent compositions comprising a mixture of one or moresurfactants with a unique builder for said compositions which comprisesa crosslinked, water-insoluble copolymer of at least one C -C olefin andat least one polycarboxyl vinyl monomer; said crosslinked,water-insoluble copolymer being a water-swellable, gel-forming material.

16 Claims, No Drawings METHOD OF TREATING PERMEABLE FORMATIONSBACKGROUND OF THE INVENTION It is often desirous to prevent the flow offluids through certain zones of geologic formations, e.g.,

aquifers. For example, fluid producing formations encountered whendrilling petroleum wells, when creating shafts, tunnels and other typesof underground passageways, such as, when connecting undergroundpassageways with the surface of the earth can cause serious problems.Also, foundations upon which large buildings or dams are being preparedusually must be impermeable to the flow of water and the like. In thepast various methods have been employed in an attempt to prevent suchflow from or'through certain zones of such formations. For example,grouting material has been forced'into natural occurring fissures andfractures in such formations to partially prevent the flow of fluids.Likewise, such formations have'been hydraulically fractured to produceadditional fractures which are then-grouted. However, these means arenot always successful because such formations do not always containnatural occuring fractures which can be grouted-to prevent the flow offluids. Likewise, a suffi-- cient amount'of hydraulic pressure cannotalways be exerted on such formations to provide a sufficient number ofadditional fractures for effectively shutting off fluid flow. Also,since the drilling is performed in relatively dry formations (aftertreatment thereof by the present invention) air drilling can be employedinstead of circulating drilling muds. This can constitute substantialsavings in the operation.

SUMMARY OF THE INVENTION In the present method; a permeable formation ispenetrated by at least one treatment borehole. A sufficient amount of ablasting agent .is disposed in the borehole contiguous to the zone ofthe formation desired to be grouted. The explosive is detonated toprovide a multiplicity of fractures extending radially away from saidborehole. Rubble, if any, may then be removed from the borehole and thefractures grouted to reduce the permeability of the formation in thefractured and grouted zone. The permeable formations may be producingundesirable fluids, e.g., an aquifer, which it may be desired to reduce,and/or it may be a formation through which the flow of fluids is to berestricted, e.g., supporting formations upon which structures are to bebuilt.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1-4 illustrate one embodiment ofthe present invention where a fluid bearing formation is treated by themethod of the present invention to prevent the flow of fluid into alarge diameter shaft.

FIG. 5 illustrates the configuration of the drilling pattern for themethod described in Example 2.

FIGS. 6 and 7 illustrate still another embodiment of the presentinvention wherein a large underground area is treated by the 'method ofthe present invention to prevent the flow of fluids through formationsforming support for a structure, e.g., a dam.

FIGS. 8 and 9 illustrate another embodiment of the an angled spiralconfiguration.

FIGS. 10 and 11 illustrate two embodiments of the present invention asapplied to the treatment of a fluid bearing formation through which asubstantially horizontal tunnel is to be prepared. In FIG. 10 thetreatment boreholes are drilled down from the surface of the earth andthe formation is fractured and grouted by the method of the presentinvention to provide a grouted zone through which the tunnel can beprepared. In FIG. 11 the treatment bore(s) (more than one if necessary)is drilled ahead of tunnel and the fluid bearing formation treated in alike manner. The number of treatment boreholes shown is merelyillustrative, the exact number employed is dependent on the size of theformation to be treated, the type of explosive employed and other likeconditions.

DETAILED DESCRIPTION OF THE INVENTION In the practice of the presentinvention the permeability of a permeable geologic formation penetratedby at least one treatment borehole is reduced in the following manner. Apredetermined amount of a blasting agent is disposed within thetreatment borehole(s) .contiguous to the permeable formation desired tobe treated. The blasting agent is detonated producing multiple fracturesin said formation extending radially away from the treatment borehole.In many instances intersecting, cross-connecting fractures are alsoproduced. Rubble, if any, is then preferably removed from the boreholeand the fractures, and, if desired, the so produced cavity is grouted toprevent the flow of fluid through the fractured zone.

The present invention can be employed to prepare openings, e.g., shafts,boreholes, tunnels, etc., which have a relatively large diameter, e.g.,afew feet or more. Because of the large diameter it may be impracticalto attempt to fracture permeable formations penetrated by such openingswith a blasting agent. In the present method, therefore, at least onesmaller treatment borehole is first drilled and the permeable formationtreated, i.e., fractured and grouted, employ ing the treatment bo eholeas the base of operation.

With reference to IGS. 1-4 one embodiment of the present invention ispracticed as follows. It is desired to sink an opening, e.g., shaft,borehole, etc., having a final diameter 10, for example to connect withan underground passageway 17. At least one smaller treatment borehole 11 is first provided, e.g., drilled, approximately concentric and alongthe vertical axis of the desired hole 10. When the smaller treatmentborehole l1 penetrates a fluid producing formation 12, FIG. 2, e.g., anaquifer, drilling is temporarily stopped. A predetermined amount of ablasting agent 13 is disposed in the treatment borehole 11 contiguous,i.e., adjacent, to the fluid producing formation 12. As will be morefully discussed hereinafter a sufficient amount of a particular blastingagent is provided so that upon the detonation thereof fractures will beproduced in the fluid bearing formation 12 extending a known distancefrom and around the treatment borehole 1 1. In this embodiment thefractures should extend a distance greater than the diameter of thefinal hole 10. The blasting agent 13 is then detonated to produce thefractures 14, FIG. 3, extending radially away from the treatmentborehole 11 and a distance greater than the diameter of the final hole10, FIG. 3. The fractures are then grouted with a suitable material 15in a manner should have a molecular weight prior to crosslinking, asexpressed in terms of their relative viscosity as determined, at 25 C.,with a 1 percent solution of the copolymer in N-methylpyrrolidone, of atleast about 1.05. Thus, the use of copolymers having a substantiallylower molecular weight is undesirable inasmuch as large quantities ofcrosslinking agent will be required in order to convert them into theirrequired water-insoluble albeit water-swellable, gel forming form. Thoseskilled in the polymer art will have little or no difficulty inadjusting the process variables of the polymerization reaction in orderto be able to prepare the resulting copolymers so that their molecularweights are greater than the above stated minimum limit.

Since the polymeric detergent builders of this invention are mostconveniently utilized in the form of their salts, such salts, includingtheir alkali metal and ammonium salts, may be readily prepared eitherprior or subsequent to the crosslinking of these copolymers. Thus, it ismerely necessary to react the solid copolymer at ambient temperatureswith about a percent, by weight, aqueous solution of sodium, potassium,lithium, or ammonium hydroxide for a sufficient period until a swollenstructure is obtained. The latter product is then added to an alcohol inorder to precipitate out the desired copolymer salt.

As has previously been noted, the polymeric detergent builders of thisinvention must be in a water-insoluble, gel-forming crosslinked form.Thus, crosslinking of these copolymers is usually carried out as adistinct and separate step which is conducted subsequent to theirpolymerization.

More particularly, the post-polymerization, crosslinking of thesecopolymers, or their salts, involves their reaction with an effectiveconcentration of one or more reagents capable of transforming theiressentially linear configuration into a threedimensional,water-insoluble network. Preferred for this purpose are the compoundshaving the structure:

wherein R represents an aliphatic or aromatic hydrocarbon group havingfrom about two to 30 carbon atoms and which may contain one or morehetero atoms such, for example, as an oxygen, sulfur or nitrogen atom; Xrepresents a primary or secondary OH group; anisocyanate,i.e.,-N C O,group,an epoxy group; an ethyleneirnine a primary or secondary -Sl-I,-NHR group wherein R represents hydrogen, an alkyl or a substitutedalkyl group having from 1 to 12 carbon atoms which may be linear orbranched and wherein suitable substituent groups for said alkyl groupsmay comprise halo, nitro, alkoxy, cyano, acyl and the like and nrepresents an integer having a value of from about 2 to 100.

Exemplary of the applicable crosslinking agents conforming to the aboveformula are: glycols such as ethylene glycol, the propane glycols, thebutane glycols, the pentane glycols, the hexane glycols, the cyclohexaneglycols, the heptane glycols, the octane glycols, the nonane glycols,the decane glycols, the undecane glycols, the dodecane glycols and thexylene glycols; the triols such as glycerol, trimethylol-propane, thebutane triols, the pentane triols, the hexane triols, the cyclohexanetriols, the heptane triols, the octane triols, the nonane triols, thedecane triols, the undecane triols, the dodecane triols, the tetrolssuch as the butane tetrols, the pentane tetrols includingpentaerythritol, the hexane tetrols, the cyclohexane tetrols, theheptane tetrols, the octane tetrols, the nonane tetrols, the decanetetrols and, the undecane tetrols; the pentitols such as arabitol,adonitol, xylitol and rhamnitol; the hexitols such as glucose, mannitol,sorbitol and dulcitol; and, the heptitols such as pereseitol andvolernitol.

Also applicable are the higher polyhydric alcohols of the saccharidetypes such as raffinose, sucrose, galactose, mannose, gulose, idose,tolose, allose, fructose, sorbose, and the acetylenic and olefinicunsaturated glycols such as 2-butyne-l,4-diol, 3,6-dihydroxycyclohexeneand dipropenylglycol; polyhydric amines such as ethylene diamine,trimethylene diamine, tetramethylene diamine, pentamethylene diamine andhexamethylene diamine; the cyclohexane diamines, heptamethylene diamine,octamethylene diamine, nonamethylene diamine, decamethylene diamine,ophenylene diamine, m-phenylene diamine, p-phenylene diamine, diethylenetriamine, triethylene tetraamine, ethanolamine, tetraethylene pentamine,pentaethylene hexamine, polyethyleneimine, the N,N'dialkyl or diarylethylene diamines where the alkyl or the aryl groups have a combinedvalue of from two to 12 carbon atoms and nitrilo bis-propylaminepolyhydric thioglycols such as ethylene dithioglycol, propylenedithioglycol, trimethylene dithioglycol, tetramethylene dithioglycol,pentamethylene dithioglycol and the like; polyhydric amino alcohols suchas diethanolamine, 2,3-dihydroxypropyl amine, N-alkyl or N-arylethanolamines wherein the alkyl group has from one to 12 carbon atoms;thio amines such as beta-mercapto ethyl amine, beta-mercapto-N-alkyl orN-aryl ethyl amines wherein diisocyanates such as tolylene diisocyanate,hexarnethylene diisocyanate, methylene, bis-(p-phenyl isocyanate) andthe like; and, unsaturated organic alcohols such as allyl alcohol andl-dodecene-lO-ol, and the like. In addition, certain hydroxyl containingpolymeric materials, such as polyvinyl alcohol, may also be used ascrosslinking agents.

From the above listed group of crosslinking agents, it is preferred toemploy (1) alkylene polyamines such, for example as diethylene triamine,triethylene triamine, triethylene tetramine and tetraethylene pentamine;or (2) alpha, omega-polymethylene diamines such, for example, asethylene diamine, hexamethylene diamine, octamethylene diamine ando-phenylene diamine. The actual crosslinking reaction may be conductedby admixing a solution of the copolymer, which may be in its anhydride,acid or salt form or as a copolymer salt mixture thereof, with asolution containing an effective concentration of the selectedcrosslinking agent and thereupon heating the resulting mixture, withagitation, at a temperature of from about 25 to C. and for a period offrom about 5 minutes to 24 hours. The precise details of time,temperature and concentration of crosslinking agent will, of course, bedependent upon such factors as the particular copolymer and crosslinkingagent which are being reacted. However, in most instances the weightratio of the copolymer to the crosslinking agent will range from about20:1 to about 500: 1.

Regardless of the manner in which the crosslinking of the copolymer isachieved, itis essential that the crosslinking reaction should proceedto a degree which is sufficient to result in the preparation of anessentially water-insoluble rather than a water soluble material.Accordingly, the crosslinking reaction should yield a productcharacterized by its ability to form a threedimensional,water-insoluble, gel-network when introduced into an aqueous mediumwherein it will appear as a translucent or transparent suspension whichmay or may not be in the colloidal form. This threedimensional gelnetwork is highly swellable under the alkaline conditions encounteredwhen it is used as part of a detergent composition but it does not,however, go into solution since its gel-network remains insoluble. Thus,it is to be stressed at this point, that the novel detergent builders ofthis invention must be both crosslinked and yieldwater-insoluble gelstructures in an aqueous medium. As be seen, it is thisuniquecombination of properties which serves to distinguish these novelbuilders from the polymeric detergent builders of the prior art which,as has been noted, were in all cases water soluble regardless of whetherthey were in linear or crosslinked form. It mayalso be noted that whilesuch crosslinked, water-insoluble, gel-forming copolymers of olefins andpolycarboxyl vinyl monomers have been known to those skilled in the artand are, in fact, commercially available, they have never, heretofore,been suggested for use as builders for detergent compositions. Asopposed to species forming liquids on dissolution, the swollen orpartially swollen crosslinked polymer gels produced upon the admixturewith water of the polymer builders of this invention, may technically bedescribed as solids since they can support their own weight and have acertain degree of rigidity. after the dispersed particles are coalescedas, for example, by centrifugation, or if there is a sufiicientconcentration present to pervade the entire available liquid. As is trueof other gels, the detergent builders of this invention may berheologically characterized by the absence of steady flow upon beingsubjected to slight stresses.

' Such behavior in binary systems, even where a very high content of aliquid solvent is present, is accounted for by the presence in a gel ofa three-dimensional network formed by the solute which thus serves tohold the liquid solvent entrapped therein.

While detergent builders comprising essentially water-soluble, linearpolymers or essentially water soluble polymers containing branchesformed by means of partial crosslinking, or other means, may provideresults equivalent to inorganic phosphates such as sodiumtripolyphosphate, the novel crosslinked, water-insoluble detergentbuilders of this invention will, on the other hand, generally provideresults which are significantly better than those attainable with theinorganic phosphates. These superior results have been found to bedirectly attributable to the water-insoluble, three dimensional gelstructure which they provide upon introduction into an aqueous medium.

In some cases, the gel structure of the detergent builders of thisinvention, when dispersed in an aqueous medium, will pervade 100 percentof the liquid volume whereas in other cases it will pervade only part ofit. This factor, known as the gel volume percent, provides a convenientmeans for further characterizing these novel detergent builders. Thus,the gel volume percent of these builders may vary as a result of theinfluence of such factors as the individual swelling characteristics ofthe particular crosslinked copolymer or the absolute amount of gel thatis present. Moreover, there is a definite and highly significantcorrelation between the gel volume percent of these builders and theirefficiency as detergent builders. This relates to the fact that theefficiency of these polymeric detergent builders is proportional to theamount of gel which they yield in an aqueous medium, i.e., the gelvolume percent of these polymeric builders is related to theirdetergency or cleaning power.

In determining gel volume percent, the following procedure is used: TestNo. l

A 1 percent, by weight, aqueous suspension of the detergent builder isprepared by mixing one gram of the solid detergent builder and 99 gramsof distilled water which has been preheated to about 60 C. In somecases, as when the crosslinked polymeric detergent builder is in itsanhydride form, the anhydride linkages must be hydrolyzed prior todetermining the gel volume percent and this may be accomplished bywarming the anhydride copolymer, with agitation, in an alkaline, aqueousmedium having a pH of about 11 until full swelling is attained. Ingeneral, the process takes from 2 to 24 hours and during this periodcare must be exercised in order to prevent loss of water throughevaporation.

The pH of the resulting suspension is then adjusted to a level of aboutllfllS with a 20 percent, by weight, solution of sodium hydroxidewhereupon it is cooled to room temperature, homogenized by agitation andpoured into a 50 milliliter graduated centrifuge tube. The fluid iscentrifuged at 2,500 rpm in a centifuge in which the horizontal distancebetween the end of the centifuge tube and its rotating center axis is nomore than 19 centimeters. After 30 minutes, the line of demarcationseparating the gel and the soluble phases is read and the gel-volumepercent is calculated according to the following formula:

Gel volume percent Volume of gel Total volume of aqueous mixture A gelvolume of at least 5 volume-percent indicates that a crosslinked,water-insoluble, but water-swellable copolymer gel is present. However,the best crosslinked copolymers for use as detergent builders in thecompositions of this invention are those which have a gel volume greaterthan 50 volume-percent with an optimum gel volume of 100 percent; all ofthese gel volumes being determined at a pH of about I 1.

In those cases where there is no visible line of demarcation separatingthe gel and soluble phases, whether this is due to the presence of 100percent gel volume or to the complete absence of any gel, a second testmust be performed on the same aqueous system in order to determine thegel volume percent of the polymeric builder dispersed therein.

Test No. 2

Under agitation, the same gel suspension, while still in the samegraduated centrifuge tube as used in Test No. 1, is acidified by thedropwise addition of an approximately 37 percent, by weight, aqueoussolution of HCl. Acidification and agitation are continued until thefirst sign of permanent turbidity is observed thereby signallingincipient coagulation. Additional HCl solution is then added dropwisewith agitation being applied after adding each drop so as to reachcoagulation of the gel. The recognition of the onset of coagulation maybe facilitated by the observation of the air bubbles formed during themixing of the gel suspension which is accomplished by shaking. Smallbubbles do not rise in the gelled medium, they rise only after the onsetof the coagulation. The commencement of the rising of the bubbles is,therefore, the endpoint of the test, at which time centrifugation maynow be begun. It is to be noted, that the addition of l-lCl should notexceed the endpoint because the gel volume percent decreases as the pHis lowered. The centrifugation is then repeated at 2,500 rpm for 30minutes as described above in Test No. l. The gel volume within the tubeand the pH of the supernatant are then recorded and the gel volumepercent of the total solution is calculated by means of the formula setforth, in Test 1 In the event that the addition, in Test No. 2, of theHCl solution to the gel suspension does not produce any permanentturbidity, it may be concluded that the sample is not a crosslinkedmaterial or, if crosslinked, that it is water soluble and is, therefore,unsuitable for use as a detergent builder in the compositions of thepresent invention. Moreover, as has been noted, only those crosslinkedwater insoluble polymeric builders capable of exhibiting a gel volume ofat least about 5 and, preferably, at least about 50 percent, asdetermined by Test No. l or Test No. 2 are suitable for use in thedetergent compositions of this invention. Optimum results are, however,obtained by the use of detergent builders having a gel volume of 100percent, as determined by Test No. 1.

In using the above described builders to prepare detergent compositions,it is merely necessary to intimately admix one or more of these builderswith one or more surfactants, i.e., surface active agents. The selectedsurfactant may be an anionic, nonionic, zwitterionic or an ampholytic,i.e., amphoteric, surfactant or one may employ a mixture of any two ormore surfactants which may be of the same or of two or more differenttypes, e.g., a blend of an anionic and nonionic surfactant.

Anionic surface active compounds can be broadly described as compoundswhich contain hydrophilic and lipophilic groups with the hydrophilicgroup containing at least one negatively charged moiety. These compoundsinclude sulfated or sulfonated alkyl, aryl and alkyl aryl hydrocarbonsand alkali metal and ammonium salts thereof, for example, sodium saltsof long chain alkyl sulfates, sodium salts of alkyl naphthalene sulfonicacids, sodium salts of sulfonated abietenes, sodium salts of alkylbenzene sulfonic acids particularly those in which the alkyl groupcontains from eight to 24 carbon atoms; sodium salts of sulfonatedmineral oils and sodium salts of sulfo-succinic acid esters such assodium dioctyl sulfo-succinate.

Advantageous anionic surfactants include the higher alkyl aryl sulfonicacids and their alkali metal, ammonium and alkaline earth metal saltssuch as for example sodium dodecyl benzene sulfonate, sodium tridecylsulfonate, magnesium dodecyl benzene sulfonate, potassium tetradecylbenzene sulfonate, ammonium dodecyl toluene sulfonate, lithiumpentadecyl benzene sulfonate, sodium dioctyl benzene sulfonate, disodiumdodecyl benzene disulfonate, disodium di-isopropyl naphthalenedisulfonate and the like as well as the alkali metal salt of alkyl aryl(sulfothioic acid) ethers and the alkyl thiosulfuric acid, etc.Preferred anionic organic surface active agents are, as notedhereinbefore, sodium salts of alkyl benzene sulfonic acids andparticularly preferred sodium salts of alkyl benzene sulfonic acids arethose in which the alkyl group or radical contains 10 to 18 carbon atomsin a straight (i.e., unbranched) chain.

Nonionic surface active compounds can be broadly described as compoundswhich do not ionize but usually acquire hydrophilic characteristics froman oxygenated side chain, such as polyoxyethylene, while the lipophilicpart of the molecule may come from fatty acids, phenols, alcohols,amides or amines. Examples of nonionic surfactants include productsformed by condensing one or more alkylene oxides of two to four carbonatoms, such as ethylene oxide or propylene 0xide, preferably ethyleneoxide alone or with other alkylene oxides, with a relatively hydrophobicor lipophilic compound such as a fatty alcohol, fatty acid, sterol, afatty glyceride, a fatty amine, an aryl amine, a fatty mercaptan, talloil, etc. Nonionic surface active agents also include those productsproduced by condensing one or more relatively lower alkyl alcohol amines(such as methanolamine, ethanolamine, propanolarnine, etc.) with a fattyacid such as lauric acid, cetyl acid, tall oil fatty acid, abietic acid,etc.

Still other nonionic surface active compounds include the amine oxidesand phosphine oxides and preferably the unsymmetrical tn'alkyl amineoxides and phosphine oxides wherein two of the alkyl groups are loweralkyl groups (one to four carbon atoms) and the other alkyl group is ahigher alkyl group (eight to 18 carbon atoms). Examples includedimethyldodecylamine oxide, dimethyl dodecylphosphine oxide, dimethyltetradecyl amine oxide, dimethyltetradecyl phosphine oxide,diethylhexadecylamine oxide, diethylhexadecylphosphine oxide and thelike.

Particularly advantageous nonionic surface active agents arecondensation products of a hydrophobic compound having at least oneactive hydrogen atom and a lower alkylene oxide (for example thecondensation product of an aliphatic alcohol containing from about eightto about 18 carbon atoms) and from about 3 to about 30 moles of ethyleneoxide per mol of the alcohol, or the condensation product of an alkylphenol containing from about eight to about 18 carbon atoms in the alkylgroup and from about three to about 30 mols of ethylene oxide per mol ofalkyl phenol. Other advantageous nonionic detergents includecondensation products of ethylene oxide with a hydrophobic compoundformed by condensing propylene oxide with propylene glycol.

Amphoteric or ampholytic surface active compounds can be broadlydescribed as compounds which have both anionic and cationic groups inthe same molecule. Such compounds may be grouped into classescorresponding to the nature of the anionicforming group, which isusually carboxy, sulfo or sulfato. Examples of such compounds includesodium N-coco beta amino propionate, sodium N-tallow beta aminodipropionate, sodium N-lauryl beta iminodipropionate and the like.

Zwitterionic surfactants can be broadly described as derivatives ofaliphatic quartemary ammonium compounds in which the aliphatic radicalmay be straight chain or branched and wherein one of the aliphaticsubstituents contains from about eight to 18 carbon atoms and onecontains an anionic water solubilizing group. Examples of compoundsfalling within this definition are 3-(N,N-dimethyl-N-hexadecylammonio)propane-l-sulfonate and3-(N,N-dimethyl-N-hexadecylammonio)-2-hydroxypropane-1-sulfonate whichare especially preferred for their excellent cool water detergencycharacteristics.

Additional representatives of compounds exemplary of each of the abovedescribed types of surfactants are given on Pages 33-269 of McCutcheonsDetergents and Emulsifiers, 1969 Annual published in 1969 by John W.'McCutcheon, Inc., Morristown, New Jersey which is here incorporated byreference.

With respect to proportions, the concentration of the builders of thisinvention which is required to be blended with one or more surfactantsin order to prepare an operable detergent composition will varydepending upon such factors as the end use, type of surfactantsutilized, pH conditions and the like. Thus, these novel builders can beemployed in detergent compositions in any desired proportions which areeffective, i.e., any concentration which enhances the detergencycharacteristics of the selected surfactants. In general, however, theratio of builder to surfactant will vary from about 1:10 to about :1with optimum results being obtained with aratio of builder tosurfactants of from about 1:2 to about 5: 1; the latter proportionsbeing designed for the use of the resulting detergent compositions at apH of from about 9 to 12 and preferably at from about 9.5 to 1 1.5.

The detergent compositions of this invention may be prepared in any ofthe commercially desirable forms including in the bar, granular, flake,liquid and tablet forms.

If desired, the novel polymeric detergent builders of this invention maybe advantageously combined with other detergent builders which willfunction as supplementary builders. Such supplementary builders includethe conventional alkali metal polyphosphates, i.e., thetripolyphosphates and pyrophosphates such as sodium tripolyphosphate,tetrasodium pyrophosphate, tetrapotassium phosphate, disodiumpyrophosphate and the like; the amino polycarboxylic acids and saltssuch as the sodium, potassium and ammonium salts of nitrilotriaceticacid, the sodium, potassium and ammonium salts of aminotri(methylenephosphonic acid), as well as the free acid; and, thediphosphonic acids and salts such as methylene diphosphonic acid and 1-hydroxy, ethylidene diphosphonic acid. In addition, the detergentcompositions of this invention may also contain various optionaladjuncts such as foam boosters, dedusting agents, soil anti-redepositionagents, anticorrosion agents, anti-tarnishing agents, perfumes,germidical agents and optical brighteners.

In actual use, it is suggested that the detergent compositions of thisinvention be dispersed in water so that the resulting aqueous dispersionwill contain an effective concentration of the novel crosslinked, waterinsoluble, gel-forming copolymer builder in the range of from about 0.07to 7.0 percent, by weight. For best results, the water should be at atemperature in the range of from about 20 to C.

The following examples will further illustrate the embodiment of thisinvention. In these examples all parts given are by weight unlessotherwise noted.

EXAMPLE I This example provides a comparison between a number of thecrosslinked, water-insoluble, gel-forming detergent builders of thisinvention and: (l) a polyphosphate detergent builder, i.e., sodiumtripolyphosphate (STPP) and (2) an uncrosslinked, i.e., a linear, watersoluble ethylenezmaleic anhydride copolymer.

The various builders are compared with respect to the gel volumepercent, as detemiined by means of the above described procedure, aswell as with respect to their actual cleaning efficiency as expressed interms of the results obtained in the change in whiteness, i.e., the (AW), test. This washing test is conducted by comparing the whiteness of astandard 5 X 5 inches soiled cloth, sold by the American ConditioningHouse as ACH-l 15A, both before and after being washed with theparticular detergent composition which is being evaluated. In order toprovide uniform conditions the cloths are washed with a standarddetergent formulation, as described below, in a standard washer, such asthe Tergetometer sold by the United States Testing Co., Inc. at aninitial pH of about 10.5, a rate of agitation of 145 rpm and atemperature of C. for a period of 15 minutes. A 5 minute rinse cycle, atambient temperature, is provided for the cloths whereupon they aresqueezed water free, air dried and ironed. The reflectance or whitenessof the cloth samples is measured, both before and after the washingprocedure, on a color difference meter such as a D-25 Hunter ColorDifference Meter, sold by Hunter Associates Laboratory, Inc. Thus, theefficacy of the detergent builder is correlated to the absolute value ofthe change in whiteness or (A W) which is calculated as follows:

where W, is the whiteness value, or reflectance, after washing and W isthe whiteness value before washing. Thus, a higher value for A W) isindicative of a more efficient builder. In general, AW) values arereproducible within i 2 units.

The standard detergent composition used in the above described testcontains the following ingredients:

Parts Orvus AB" (Anionic surfactant) 45.0 Na SO (ionic strength control& filler) 8.5 Na,SiO, (corrosion inhibitor) 5.0 NaJQO (threshold agent)0.8 Carboxymethyl cellulose (soil antiredeposition agent) 0.7 Detergentbuilder 40.0

A mixture containing 43%, by weight, Na,SO,; 15%, by weight, NaCl; 1%,by weight, water, and, 40%, by weight, of sodiumdodecylbenzenesulfonate.

In this washing test, the concentration of the above described detergentcomposition is at 2.5 g. per liter of water containing 175 ppm ofhardness as CaCO The detergent builders which are evaluated in thismanner are described in Table I, hereinbelow.

TABLE I Builder No. Composition Control No detergent builder present 1STPP 2 A water soluble, uncrosslinked, i.e.

linear, -l:1, by mole, ethylenezmaleic anhydride copolymer having aviscosity of 7.0 cps when detennined with a 2% aqueous solution as soldby the Monsanto Company as "EMA-31 3 The water-insoluble, mixture ofmonoand disodium salts of a -l:1, by mole, ethylenezmaleic acidcopolymer prepared by crosslinking EMA-3 l with 20%, by wt., ofdiethylene triamine (DETA) and then hydrolyzing the crosslinkedcopolymer with 10%, by wt., of NaOH.

4 The water-insoluble mixture of monand disodium salts of a -l:l bymole, ethylenezmaleic acid copolymer prepared by crosslinking "EMA-31"with 0.8%, by wt., of DETA and then hydrolyzing the crosslinkedcopolymer with 10%, by wt., of NaOl-l.

5 The water-insoluble mixture of monoand disodium salts of a -l:l, bymole, ethylenezmaleic acid copolymer having a viscosity of 640 cps whendetermined with a 2% aqueous solution as sold by Monsanto Company asEMA-54."

6 A water-insoluble, crosslinked -1:1, by mole, ethylenezmaleicanhydride copolymer sold by the Monsanto Company as "EMA- 61" and havinga viscosity of 100 cps when determined with a 2% aqueous solution.

7 A water insoluble, crosslinked 1:1, by mole ethylenezmaleic anhydridecopolymer sold by the Monsanto Company as EMA- 71" and having aviscosity of 960 cps when determined with a 2% aqueous solution.

8 A water insoluble, crosslinked 1:1, by mole, ethylenezmaleic anhydridecopolymer sold by the Monsanto Company as EMA 81" and having a viscosityof 1,100 when determined with a 2% aqueous solution.

9 A water insoluble, crosslinked 1:1, by mole, ethylene:maleic anhydridecopolymer sold by the Monsanto Company as EMA 91" and having a viscosityof 8,500 when determined with a 2% aqueous solution.

Table 11, hereinbelow, provides the results of the change in whitenesstest AW) for the standard detergent compositions containing each of theabove described builders as well as for a control composition which doesnot contain any builders. The table also provides a gel volume percentvalue for each of the various builders.

LII

TABLE II Builder Test No. 1 Test No. 2

No. (AW) Gel Vol.% pH Gel Vol.% pH

Control 37.4 1 47.0 0 10.5 0 0.6 2 46.3 0 1 1 O 0.5 3 46.1 4.8 1 1 4.63.7 4 58.3 100.0 11 38.0 4.0 5 51.5 100.0 11 15.0 2.5 6 54.4 100.0 10.840.0 3.6 7 57.0 100.0 11.5 56.0 3.6 8 57.5 100.0 11.5 50.0 3.2 9 58.3100.0 10.8 54.0 3.5

With respect to the A W) values, the above given data shows that thevalue for this factor which is obtained for the builder-free control was37.4. Accordingly, any detergent composition whose A W) value wasgreater than 37.4 would be considered efficacious. In this respect, thedata reveal that the use of a linear copolymer provides detergencyresults which are approximately equal to those attained with STPPwhereas all of the crosslinked copolymers with a gel volume greater than5, i.e., Nos. 4-9, displayed superior results as detergent builders. Onthe other hand, Builder No. 3, while crosslinked, had a gel volumepercent of only 4.8 and was, therefore,no better than either STPP or thelinear copolymer represented by Builder No. 2.

The data also reveal the existence of an inverse relationship betweenthe A W) value of a detergent composition and the extent to which itspolymeric detergent builder has been crosslinked. Thus, where a buildersuch as No. 4 has been crosslinked with only 0.8 percent of DETA, it hasthe rather high AW) value of 58.3. On the other hand, when the identicalcopolymer salt is excessively crosslinked with 20 percent of DETA, i.e.,Builder No. 3, its A W) value is reduced to only 46.1. From the latterresults, it is apparent that neither inadequate nor excessivecrosslinking will yield products which provide A W) values superior tothose attainable with STPP. Thus, superior washing action on the part ofthese crosslinked copolymers can only be obtained with an optimum degreeof crosslinking as is found, for example, in Builder No. 4 which hasbeen crosslinked only to the extent necessary to provide it with aninsoluble but highly swellable gel structure upon being introduced intoan aqueous alkaline medium.

EXAMPLE II The superiority,as a detergent builder, of a water-insoluble,water swellable, gel forming copolymer fraction over a crosslinked butstill water-soluble fraction of the identical copolymer is illustratedin this example.

As the starting material, there is used the commercially available,crosslinked lzl, by mole, ethylenezmaleic anhydride copolymer sold bythe Monsanto Company as EMA-91." Thus, 10 grams of EMA-91 are introducedinto 990 grams of preheated distilled water, and the resultingsuspension is maintained at 55-60 C. for 3 hours under vigorousstirring. The resulting viscous fluid is then centrifuged for 4 hours atabout 2,500 rpm in four 200 ml cuvettes. At the end of thecentrifugation, two distinct and separate phases are found in eachcuvette, the lower phase being an essentially opaque, greyishwhite,waterinsoluble gel of about 55 volrpercent while the upper phase is acrystal clear liquid of about 45 vol-percent. The clear upper phase isseparated by means of a syringe whereupon the solids content of eachphase is determined by evaporation in air followed by 16 hours of vacuumdrying at 75 C. Accordingly, the amount of each fraction in the drycopolymer is as follows:

82.7 wt.% of the insoluble gel forming material, and

17.3 wt.% of the soluble fraction.

A portion of each fraction is then subjected to the above describedstandard washing test and is also compared to the commercially availablenon-crosslinked, linear==lz1 ethylenezmaleic anhydride copolymer EMA-3 1sold by the Monsanto Co. Table III, hereinbelow, presents the results ofthese washing tests, revealing that the soluble phase obtained by thefractionation of crosslinked copolymer shows practically no improvement,as a detergent builder, over the use of a non-crosslinked, linearcopolymer, i.e., EMA-31. On'the other hand, the insoluble, waterswellable three dimensional gel fraction displays a remarkably highdegree of efficiency as a detergent builder.

TABLE III AW) Values Water: insoluble Unfrac- Water- Gel FrationatedSoluble ction EMA- Fraction of EMA 9l ofEMA 9i Builder EMA-31 (Cross -9l(crocross- Conc. in (Linear linked -sslinked linked Wash Copoly- Copoly-Copoly- Copoly- Water STP mer) mer) mer) mer) l g/liter 46.5 46.3 58.258.3 1% g/liter 43.0 55.3 47.6 55.3

EXAMPLE III This example illustrates the preparation of a 1:1, by mole,propylenezmaleic anhydride copolymer suitable for use in preparing thenovel detergent builders of this invention.

A mixture of 200 grams of maleic anhydride and 700 milliliters ofacetone is charged into a 3-liter Parr bomb equipped with a gas inletvalve, a valve for the introduction of initiator solution and athermocouple well. After degassing in a dry-ice acetone bath, a total of20 grams of propylene is introduced into the Parr bomb. The Parr bomb isthen heated to a temperature of about 84-85 C. and 166 milliliters of a4 percent, by weight, solution of benzoyl peroxide in acetone is thenintroduced by means of a metering pump over a period of 5 1% hours. Thereaction mixture is heated at this temperature for an additional 4 5hours and, after cooling to room temperature, the Parr bomb is ventedand the reaction mixture precipitated, with agitation, into 8-liters ofdiethyl ether. After drying, the above described copolymer is obtained.It has a relative viscosity in excess of 1.05 as determined by means ofthe above described procedure.

EXAMPLE IV This example illustrates the conversion of thepropylenezmaleic anhydride copolymer whose preparation was described inExample III, hereinabove, into the form of its sodium salt.

A total of 5 grams of the copolymer of Example III is treated with anexcess of a 10 percent, by weight, aqueous sodium hydroxide solution.After complete dissolution is achieved, the polymer solution isprecipitated in methanol. The resultant sodium salt of the copolymer isthen filtered and is finally obtained in a quantitative yield. It is tobe noted that the sodium hydroxide solution converts the maleicanhydride moieties of the copolymer to the acid form and thereuponneutralizes these acid moieites to the sodium salt form.

EXAMPLE V This example illustrates the crosslinking and subsequentneutralization of the propylenezmaleic anhydride copolymer whosepreparation is described in Example [ll hereinabove.

To a solution of 5 grams of the copolymer of Example III in 50 g ofN-methylpyrrolidone there is added 10 milliliters of a solutioncontaining 1 gram of diethylenetriarnine (DETA) diluted to 100milliliters with N-methylpyrrolidone. This mixture is heated and stirredfor 1 hour at a temperature of about 90 C. yielding a viscous, opaquemixture. A drop of this mixture gives rise to swollen gel particles whenintroduced into a 10 percent, by weight, aqueous sodium hydroxidesolution thus indicating insolubility on the part of the crosslinkedcopolymer. With vigorous agitation, an excess of the sodium hydroxidesolution is then added to the balance of the crosslinked copolymer inorder to convert it into the salt form. The entire mixture is thenpoured into methanol yielding a white precipitate which is separated byfiltration and is then dried. The yield of the sodium salt of thiswater-insoluble, crosslinked, propylenezmaleic anhydride copolymer isquantitative.

This product is found to have a gel volume above 5 percent and providesexcellent results as a detergent builder on being formulated into thestandard detergent composition described in Example 1.

EXAMPLE Vl This example illustrates the preparation of another of thenovel detergent builders of this invention.

Ten grams of EMA3 l as previously described, is crosslinked by beingdissolved in 25 milliliters of acetone and the resulting solution iswarmed to a temperature of about 4555 C. To this warm solution there isthen added 8 milliliters of a solution which is made by diluting about 1gram of DETA to milliliters with acetone. Gelation occurs in a period ofabout 1 minute. The acetone solvent is then partially removed by blowinga stream of nitrogen over the mixture and the remaining solvent isremoved under vacuum. in this manner the copolymer is crosslinked with0.8 percent, by weight of DETA.

This water-insoluble product is found to have a gel volume of 100percent, as determined by Test No. l, and provides excellent results asa detergent builder on being formulated into the standard detergentcomposition described in Example I.

EXAMPLE VII This procedure illustrates the preparation of another of thenovel detergent builders of this invention.

The procedure of Example VI was repeated with the exception, in thisinstance, that only 1.8 milliliters of the acetone solution of DETA isused for the crosslinking of the ethylenetmaleic anhydride copolymer.This reaction provides a quantitative yield of the copolymer which hasbeen crosslinked with 0.18 percent, by weight, of DETA. Thiswater-insoluble product is found to have a gel volume in excess of 90percent, as determined by means of Test No. 1 and provides excellentresults as a detergent builder on being formulated into the standarddetergent composition described in Example 1.

EXAMPLE VHI This example illustrates the preparation of 1:1, by mole,propylenezitaconic anhydride copolymer suitable for use in preparing thenovel detergent builders of this invention.

In preparing this copolymer, the procedure of Example III is repeatedwith the exception, in this instance, that an equal amount, on a molarbasis, of itaconic anhydride is substituted for the maleic anhydride.The resulting copolymer has a relative viscosity in excess of 1.05 asdetermined under the above described conditions.

EXAMPLE IX EXAMPLE X This example illustrates the preparation of anothercopolymer suitable for use in preparing the novel detergent builders ofthis invention.

Thus, a =lzl, by mole, ethylenezcitraconic anhydride copolymer isprepared utilizing the polymeriza tion procedures of Example III withthe exception, in this instance, that ethylene is substituted for thepropylene and citraconic anhydride is used in place of the maleicanhydride. The resulting copolymer has a relative viscosity in excess of1.05 as determined under the above described conditions.

EXAMPLE XI This example illustrates the crosslinking of the lzl, bymole, ethylenezcitraconic anhydride copolymer of Example X.

Thus, the crosslinking procedure of Example VI is followed with theexception, in this instance, that the copolymer of Example X issubstituted for the ethylenezmaleic anhydride copolymer. By this means,a

quantitative yield of the water-insoluble, crosslinked copolymer isobtained. It is found to have a gel volume of greater than 5 percent andprovides excellent results as a builder on being formulated into thestandard detergent composition described in Example 1.

Variations may be made in proportions, procedures and materials withoutdeparting from the scope of this invention as defined in the followingclaims.

What is claimed is:

l. A detergent composition consisting essentially of a mixture of:

a. From I to about 2 parts by weight of at least one surfactant selectedfrom the group consisting of anionic, nonionic, zwitterionic andampholytic surfactant and mixtures thereof; and as a builder for saiddetergent composition;

. From about 5 to about 1 part by weight of an alkali metal or ammoniumsalt of a crosslinked, water-insoluble copolymer of from about 20 toabout mole percent of at least one olefin having two to 3 carbon atoms,or mixtures thereof, and from about 80 to about 20 mole percent of atleast one polycarboxyl vinyl monomer selected from the group consistingof maleic, fumaric, itaconic, aconitic, methylene malonic, mesaconic,3-butene-l,2,3-tricarboxylic and citraconic acids, anhydrides, theiralkali metal or ammonium salts or mixtures thereof; said crosslinkedcopolymer being water swellable and capable of forming a gel whenintroduced into an aqueous medium and having a relative viscosity, priorto crosslinking, of at least 1.05 as a l percent solution inN-methylpyrrolidone at 25 C, and wherein said copolymer is crosslinkedwith a crosslinking agent having the structure:

wherein R is an aliphatic or aromatic hydrocarbon having from about twoto 30 carbon atoms; x is selected from the group consisting of a primaryand secondary hydroxyl, primary and secondary SI-I and -NI-IR groups, -NC 0 groups, epoxy groups and ethyleneimine groups, and wherein R isselected from the group consisting of hydrogen, alkyl groups having fromabout one to 12 carbon atoms; and, wherein n is an integer having avalue of from about 2 to 100, said crosslinking agent being employed ina weight ratio to said copolymer of from about 1:20 to about 1:500.

2. The detergent composition of claim 1, wherein said copolymer iscrosslinked with a crosslinking agent selected from the group consistingof alkylene polyamines and alpha, omega-polymethylene diarnines.

3. The detergent composition of claim 2, wherein said copolymer iscrosslinked with diethylenetriamine.

4. The detergent composition of claim 1, wherein said crosslinkedcopolymer has a gel volume of at least about 5 percent as a 1 percent byweight concentration in distilled water at a pH of 1 l.

5. The detergent composition of claim 1, wherein said polycarboxyl vinylcomonomer is maleic anhydride.

6. The detergent composition of claim 1, wherein said olefin isethylene.

7. The detergent composition of claim 1, wherein said olefin ispropylene.

8. An aqueous dispersion of the detergent composition of claim 1.

9. The detergent composition of claim 1, wherein said crosslinkedcopolymer is selected from the group consisting of the copolymer ofethylene and maleic anhydride and the copolymer of propylene and maleicanhydride;

10. A detergent composition consisting essentially of a mixture of:

a. From about 1 to about 2 parts by weight of at least one surfactantselected from the group of anionic, nonionic, zwitterionic andampholytic surfactants and mixtures thereof; and, as a builder for saiddetergent composition;

. From about 5 to about 1 part by weight of a crosslinked, waterinsoluble copolymer of from about to 80 mole percent of ethylene andfrom about 80 to 20 mole percent maleic anhydride; said crosslinkedcopolymer being water-swellable and capable of forming a gel whenintroduced into an aqueous medium, and having a relative viscosity,prior to crosslinking, of at least -1 .05 as a 1 percent solution inN-methyl-pyrrolidone at C, and a wherein said copolymer is crosslinkedwith a crosslinking agent having the structure:

wherein R is an aliphatic or aromatic hydrocarbon having from about twoto carbon atoms; x is selected said copolymer of from about 1:20 toabout 1:500.

11. The detergent composition of claim 10, wherein said copolymer iscrosslinked with a crosslinking agent selected from the group consistingof alkylene polyamines and alpha, omega-polyethylene diamines.

12. The detergent composition of claim 11, wherein said copolymer iscrosslinked with diethylenetriamine.

13. The detergent composition of claim 10, wherein said crosslinkedcopolymer has a gel volume of at least about 5 percent as a 1 percent byweight concentration in distilled water at a pH of l l.

14. The detergent composition of claim 10, wherein said crosslinkedcopolymer is in the form of an alkali metal or ammonium salt.

15. An aqueous dispersion of the detergent composition of claim 10.

16. A detergent composition consisting essentially of a relative 'scosirior to crosslinkin of 1.05 a 1 perceri t solutii m in N-methylpyrrohdone at 2 5 C., and which has been crosslinked with diethylenetriaminein a weight ratio of copolymer to crosslinking agent of about 20:1 toabout 500:1; said copolymer being water-swellable and capable of forminga gel having a gel volume of at least 5 when introduced into distilledwater in a 1 percent by weight concentration at a pH of about 1 1.

2. The detergent composition of claim 1, wherein said copolymer iscrosslinked with a crosslinking agent selected from the group consistingof alkylene polyamines and alpha, omega-polymethylene diamines.
 3. Thedetergent composition of claim 2, wherein said copolymer is crosslinkedwith diethylenetriamine.
 4. The detergent composition of claim 1,wherein said crosslinked copolymer has a gel volume of at least about 5percent as a 1 percent by weight concentration in distilled water at apH of
 11. 5. The detergent composition of claim 1, wherein saidpolycarboxyl vinyl comonomer is maleic anhydride.
 6. The detergentcomposition of claim 1, wherein said olefin is ethylene.
 7. Thedetergent composition of claim 1, wherein said olefin is propylene. 8.An aqueous dispersion of the detergent composition of claim
 9. Thedetergent composition of claim 1, wherein said crosslinked copolymer isselected from the group consisting of the copolymer of ethylene andmaleic anhydride and the copolymer of propylene and maleic anhydride.10. A detergent composition consisting essentially of a mixture of: a.From about 1 to about 2 parts by weight of at least one surfactantselected from the group of anionic, nonionic, zwitterionic andampholytic surfactants and mixtures thereof; and, as a builder for saiddetergent composition; b. From about 5 to about 1 part by weight of acrosslinked, water insoluble copolymer of from about 20 to 80 molepercent of ethylene and from about 80 to 20 mole percent maleicanhydride; said crosslinked copolymer being water-swellable and capableof forming a gel when introduced into an aqueous medium, and having arelative viscosity, prior to crosslinking, of at least 1.05 as a 1percent solution in N-methyl-pyrrolidone at 25* C, and wherein saidcopolymer is crosslinked with a crosslinking agent having the structure:R-(x)n wherein R is an aliphatic or aromatic hydrocarbon having fromabout two to 30 carbon atoms; x is selected from the group consiSting ofa primary and secondary hydroxyl, primary and secondary -SH and -NHR''groups, -N=C=O groups, epoxy groups and ethyleneimine groups, andwherein R'' is selected from the group consisting of hydrogen, alkylgroups having from about one to 12 carbon atoms; and, wherein n is aninteger having a value of from about 2 to 100, said crosslinking agentbeing employed in a weight ratio to said copolymer of from about 1:20 toabout 1:500.
 11. The detergent composition of claim 10, wherein saidcopolymer is crosslinked with a crosslinking agent selected from thegroup consisting of alkylene polyamines and alpha, omega-polyethylenediamines.
 12. The detergent composition of claim 11, wherein saidcopolymer is crosslinked with diethylenetriamine.
 13. The detergentcomposition of claim 10, wherein said crosslinked copolymer has a gelvolume of at least about 5 percent as a 1 percent by weightconcentration in distilled water at a pH of
 11. 14. The detergentcomposition of claim 10, wherein said crosslinked copolymer is in theform of an alkali metal or ammonium salt.
 15. An aqueous dispersion ofthe detergent composition of claim
 10. 16. A detergent compositionconsisting essentially of a mixture of: a. From about 1 to about 2 partsby weight of at least one surfactant selected from the group consistingof anionic, nonionic, zwitterionic and ampholytic surfactants andmixtures thereof; and, as a builder for said detergent composition; b.From about 5 to about 1 part by weight of a crosslinked, water-insolublecopolymer consisting of a copolymer of 20 to 80 mole percent ethyleneand 80 to 20 mole percent maleic anhydride which has a relativeviscosity; prior to crosslinking, of 1.05 as a 1 percent solution inN-methylpyrrolidone at 25* C., and which has been crosslinked withdiethylenetriamine in a weight ratio of copolymer to crosslinking agentof about 20:1 to about 500:1; said copolymer being water-swellable andcapable of forming a gel having a gel volume of at least 5 whenintroduced into distilled water in a 1 percent by weight concentrationat a pH of about 11.